Microbicides

ABSTRACT

When used in admixture with mancozeb, chlorothalonil, a copper salt, folpet, fluazinam or cymoxanil (it being possible for the latter to be used also together with one of the other five components), metalaxyl having a high R-enantiomer content of more than 70% by weight, or pure R-metalaxyl, exhibits a markedly increased fungicidal action against plant diseases as compared with a similar mixture in which metalaxyl is used in the form of the racemate.

[0001] The present invention relates to fungicidal two- andthree-component mixtures based on metalaxyl having an R-enantiomercontent of more than 70% by weight, and to the use thereof incontrolling and preventing Oomycetes infestation. The metalaxylcomponent is called active ingredient I.

[0002] The following fungicides may be used as the second component IIof the mixture:

[0003] IIA) mancozeb;

[0004] IIB) chlorothalonil;

[0005] IIC) a copper salt, for example CuCO₃, CuSO₄, Cu(OH)₂.CUCl₂,especially Cu(OH)₂;

[0006] IID) folpet;

[0007] IIE) fluazinam[=3-chloro-N-(3-chloro-5-trifluoromethyl-2-pyridyl)-α,α,α-trifluoro-2,6-dinitro-p-toluidine];and

[0008] IIF) cymoxanil, which can be used either on its own or inadmixture with one of the above-mentioned components IIA to IIE(three-component mixtures).

[0009] More specifically, the invention relates to mixtures comprisingmetalaxyl having an R-enantiomer content of more than 85% by weight,preferably of more than 92% by weight, and especially containing pureR-enantiomer that is substantially free of S-enantiomer.

[0010] Metalaxyl of the formula

[0011] has an asymmetric *C atom and can be resolved into theenantiomers in customary manner (GB-P.1 500 581). Since 1975 it has beenknown to those skilled in the art that the R-enantiomer is far superiorto the S-enantiomer in terms of fungicidal action and is in practiceregarded as the true mechanism of action. Commercial metalaxyl isavailable in the form of the racemate. Likewise, mixtures of metalaxylracemate with mancozeb, chlorothalonil, copper preparations, folpet,fluazinam or cymoxanil have become known commercially or otherwise.There has in the past never been any practical necessity to resolve theracemate, of which half consists of the desired R-enantiomer.

[0012] It has now been found, completely surprisingly, that R-metalaxylin pure or more than 70% form, in admixture with the fungicidalcomponents IIA to IIF, achieves a synergistically enhanced action whichin some cases exceeds that of the prior-known mixtures based on theracemate by a factor of 10. Given that half of the racemate consists ofR-enantiomer, factors of approximately 2 or, at most, 3 were to beexpected.

[0013] With this completely unexpected result, the present inventionconstitutes a very considerable enrichment of the art and represents apossible means of reducing in an environmentally protective manner thetotal amount of fungicides used for controlling Oomycetes on plants.

[0014] In addition to the two-component mixture I:II, the presentinvention relates also to a method of controlling fungi, which comprisestreating a site, for example a plant, that is infested by or threatenedwith infestation by fungi with, in any desired sequence orsimultaneously, a) component I and b) the active ingredient of formulaII.

[0015] Advantageous mixing ratios of the two active ingredients areI:II=from 10:1 to 1:100, preferably I:II=from 5:1 to 1:30. In manycases, mixtures in which the mixing ratio of the active substances I:IIis from 1:1 to 1:20, for example 2:5, 1:4, 1:8 or 1:10, areadvantageous.

[0016] The active ingredient mixtures I+II according to the inventionhave very advantageous curative, preventive and systemic fungicidalproperties for protecting cultivated plants. The active ingredientmixtures of the invention can be used to inhibit or destroy themicro-organisms which occur on plants or on parts of plants (the fruit,blossom, leaves, stems, tubers or roots) of different crops of usefulplants, while at the same time parts of plants that grow later are alsoprotected against such microorganisms. This applies especially also tomicroorganisms that have developed reduced sensitivity to metalaxyl.

[0017] The active ingredient mixtures of formulae I and II are generallyused in the form of compositions. R-metalaxyl (formula I) and the activeingredient of formula II can be applied to the area or plant to betreated simultaneously or in immediate succession, if desired togetherwith further carriers, surfactants or other application-promotingadjuvants customarily employed in formulation technology.

[0018] Suitable carriers and adjuvants can be solid or liquid and arethe substances ordinarily employed in formulation technology, e.g.natural or regenerated mineral substances, solvents, dispersants,wetting agents, tackifiers, thickeners, binders or fertilisers.

[0019] A preferred method of applying an active ingredient mixturecomprising at least one of each of the active ingredients I and II isapplication to the parts of the plants that are above the soil,especially to the leaves (foliar application). The frequency and rate ofapplication depend upon the biological and climatic living conditions ofthe pathogen. The active ingredients can, however, also penetrate theplant through the roots via the soil (systemic action) if the locus ofthe plant is impregnated with a liquid formulation or if the substancesare introduced in solid form into the soil, e.g. in the form of granules(soil application).

[0020] The compounds of the combination are used in unmodified form or,preferably, together with the adjuvants conventionally employed informulation technology, and are therefore formulated in known mannere.g. into emulsifiable concentrates, coatable pastes, directly sprayableor dilutable solutions, dilute emulsions, wettable powders, solublepowders, dusts, granules, or by encapsulation in e.g. polymersubstances. As with the nature of the compositions, the methods ofapplication, such as spraying, atomising, dusting, scattering, coatingor pouring, are chosen in accordance with the intended objectives andthe prevailing circumstances. Advantageous rates of application of theactive ingredient mixture are normally from 50 g to 1800 g of activeingredient (a.i.) per hectare, preferably from 100 g to 1000 g a.i./ha.Mixtures of R-metalaxyl (I) with mancozeb (IIA) are advantageouslyemployed at rates of application of from 100 g to 120 g of I and 1600 gof IIA.

[0021] The formulations are prepared in known manner, e.g. byhomogeneously mixing and/or grinding the active ingredients withextenders, e.g. solvents, solid carriers and, where appropriate,surface-active compounds (surfactants).

[0022] The agrochemical compositions generally comprise 0.1 to 99%,preferably 0.1 to 95%, of active ingredients of formulae I and II, 99.9to 1%, preferably 99.9 to 5%, of a solid or liquid adjuvant and 0 to25%, preferably 0.1 to 25%, of a surfactant.

[0023] Whereas commercial products will preferably be formulated asconcentrates, the end user will normally employ dilute formulations.

[0024] Suitable target crops are especially potatoes, vines, hops,maize, sugar beet, tobacco, vegetables (tomatoes, paprika, lettuce,etc.), and also bananas, natural rubber plants, as well as lawn areasand ornamentals. Other plants threatened by downy mildew have becomeknown inter alia from the literature relating to metalaxyl.

[0025] The Examples which follow serve to illustrate the invention,“active ingredient” denoting a mixture of R-metalaxyl and compound II ina specific mixing ratio. Wettable powders a) b) c) active ingredient 27%51% 75% [I:IIA = 1:4(a), 1:16(b), 2:13(c)] sodium lignosulfonate  5%  5%— sodium laurylsulfate  3% —  5% sodium diisobutylnaphthalene- —  6% 10%sulfonate octylphenol polyethylene glycol —  2% — ether (7-8 mol ofethylene oxide) highly dispersed silicic acid  5% 10% 10% kaolin 60% 26%—

[0026] The active ingredient is thoroughly mixed with the adjuvants andthe mixture is thoroughly ground in a suitable mill, affording wettablepowders which can be diluted with water to give suspensions of thedesired concentration. Emulsifiable concentrate active ingredient 10%(I:IIA, IIB, IID or IIE = 3:7) octylphenol polyethylene glycol ether(4-5 mol of ethylene oxide)  3% calcium dodecylbenzenesulfonate  3%castor oil polyglycol ether  4% (35 mol of ethylene oxide) cyclohexanone30% xylene mixture 50%

[0027] Emulsions of any required dilution, which can be used in plantprotection, can be obtained from this concentrate by dilution withwater. Extruder granules active ingredient (I:IIC = 1:4) 15% sodiumlignosulfonate  2% carboxymethylcellulose  1% kaolin 82%

[0028] The active ingredient is mixed and ground with the adjuvants, andthe mixture is moistened with water. The mixture is extruded and thendried in a stream of air. Coated granules active ingredient (I:IID =3:5)  8% polyethylene glycol (mol. wt. 200)  3% kaolin 89%

[0029] The finely ground active ingredient is uniformly applied, in amixer, to the kaolin moistened with polyethylene glycol. Non-dustycoated granules are obtained in this manner. Suspension concentrateactive ingredient (I:IIF:IIA = 3:1:7) 44% propylene glycol 10%nonylphenol polyethylene glycol ether  6% (15 mol of ethylene oxide)sodium lignosulfonate 10% carboxymethylcellulose  1% silicone oil (inthe form of a 75%  1% aqueous emulsion) water 28%

[0030] The finely ground active ingredient is intimately mixed with theadjuvants, giving a suspension concentrate from which suspensions of anydesired dilution can be obtained by dilution with water. Such dilutionscan be used to treat living plants by spraying, pouring or immersion andto protect them against infestation by microorganisms.

BIOLOGICAL EXAMPLES

[0031] Fungicides have a synergistic effect whenever the fungicidalaction of the active ingredient combination is greater than the sum ofthe actions of the active ingredients when applied individually.

[0032] The action E to be expected for a given active ingredientcombination, for example of two fungicides, obeys the so-called COLBYformula and can be calculated as follows (COLBY, L. R. “Calculatingsynergistic and antagonistic responses of herbicide combinations”. Weeds15, pages 20-22, 1967) (LIMPEL et al., 1062 “Weeds control by . . .certain combinations”. Proc. NEWCL, Vol. 16, pp. 48-53):

[0033] (mg a.i./liter=milligrams of active ingredient per liter or amultiple thereof)

[0034] X=% action by fungicide I at p mg a.i./liter

[0035] Y=% action by fungicide II at q mg a.i./liter

[0036] E=the expected action of fungicides I+II at a rate of applicationof p+q mg a.i./liter (additive action),

[0037] then according to Colby: $E = {X + Y - {\frac{X \cdot Y}{100}.}}$

[0038] If the action (O) actually observed is greater than the expectedaction, then the action of the combination is superadditive, i.e. thereis a synergistic effect.

[0039] 1) Action Against Plasmopara viticola on Vines

[0040] Small vine plants of the variety “Gutedel” are each grown in aplant-pot (diameter=6 cm) under greenhouse conditions and are sprayed inthe two-leaf stage with an active ingredient mixture prepared from anemulsifiable concentrate. The following concentrations of activeingredient are each applied to four plants:

[0041] metalaxyl racemate: 2 mg and 6 mg a.i./liter;

[0042] R-metalaxyl (100%): 0.06 mg and 0.6 mg a.i./liter;

[0043] mancozeb: 2 mg and 6 mg a.i./liter.

[0044] These dilutions are prepared in demineralised water immediatelybefore the leaves are sprayed. In order to eliminate the effect of thegas phase of the metalaxyl in the vicinity, all the plants are separatedfrom one another laterally by means of transparent plastics films andare kept in the dark for one day at 20-22° C. and about 100% relativehumidity.

[0045] The entire surface of the leaves of the plants is then uniformlysprayed to drip point with a freshly prepared sporangia suspension (120000/ml) of a strain of Plasmopara viticola that is sensitive tometalaxyl. The plants are then kept at 20-22° C. and about 100% relativehumidity for 7 days under artificial daylight of 16 hours' duration.Evaluation of the infestation is then carried out. The Tables show ineach case the average of four parallel sprayings. The expected action inthe case of mixtures is calculated according to COLBY.

[0046] Level of action of racemic metalaxyl and R-metalaxyl in admixturewith residual component mancozeb E R-enantiomer Expected O Metalaxyl ofmetalaxyl Mancozeb Mixing action Observed mg a.i./l mg a.i./l mg a.i./lratio [COLBY] action 2 12 6 24 0.06 12 0.6 18 2 0 6 20 2 2 1:1 12 27 6 23:1 24 71 2 6 1:3 40 69 6 6 1:1 30 90 0.06 2  1:33 12 43 0.6 2 1:3 18 560.06 6  1:100 30 64 0.6 6  1:10 35 91

[0047] the action of 2 mg of racemic metalaxyl in admixture with 2 mg or6 mg of mancozeb corresponds to that of 0.06 mg of R-metalaxyl inadmixture with 2 mg or 6 mg of mancozeb. This shows that the action isimproved about 30-fold when the R-enantiomer is used instead of racemicmetalaxyl.

[0048] 2) Action Against Phytophthora Infestans on Tomato Plants

[0049] Residual-protective Action

[0050] After a cultivation period of 3 weeks, tomato plants are sprayedwith a series of concentrations of a spray mixture prepared from anemulsifiable concentrate of the active ingredient mixture. The treatedplants are infected 48 hours later with a sporangia suspension of thefungus. Fungus infestation is evaluated after incubation of the infectedplants for 4 days at 90-100% relative humidity and 20° C.

[0051] The following results are obtained: R-enantiomer MancozebMetalaxyl of metalaxyl Percent [ppm a.i.] [ppm a.i.] [ppm a.i.] action20 2 18  6   0.6  0 20 2 75  6   0.6  7 Copper R-enantiomer oxychlorideMetalaxyl of metalaxyl Percent [ppm a.i.] [ppm a.i.] [ppm a.i.] action60 6 35 60 2   17.5 60 6 75 60 2 50

[0052] 3) Action Against Phytophthora on Potato Plants

[0053] Residual-protective Action

[0054] After cultivation period of 3 weeks, 2- to 3-week-old potatoplants (variety Bintje) are sprayed with a series of concentrations of aspray mixture prepared from an emulsifiable concentrate of the activeingredient mixture. The treated plants are infected 24 hours later witha sporangia suspension of the fungus. Fungus infestation is evaluatedafter incubation of the infected plants for 5 days at 90-100% relativehumidity and 20° C.

[0055] The following results are obtained: R-enantiomer MancozebMetalaxyl of metalaxyl Percent [ppm a.i.] [ppm a.i.] [ppm a.i.] action20 2 70  6   0.6 15 20 2 100   6   0.6 50 Copper R-enantiomeroxychloride Metalaxyl of metalaxyl Percent [ppm a.i.] [ppm a.i.] [ppma.i.] action 60 6   17.5 60 2  0 60 6 70 60 2 35

[0056] Similarly markedly increased actions are achieved also with theother components IIB, IID, IIE and IIF of the mixture.

[0057] Preferred mixing ratios (in amounts by weight) are:

[0058] R-metalaxyl(I):IIA (mancozeb)=1:1 to 1:20

[0059] I:IIB (chlorothalonil)=2:1 to 1:12

[0060] I:IIC (copper preparation)=5:1 to 1:30

[0061] I:IID (folpet)=3:1 to 1:10

[0062] I:IIE (fluazinam)=5:1 to 1:20

[0063] I:IIF (cymoxanil)=6:1 to 1:6

[0064] I:IIF:IIA=1 to 7:1:4 to 10

[0065] I:IIF:IID=1 to 7:1:2 to 8.

[0066] These marked increases in action with R-metalaxyl are observedalso against other Oomycetes, especially Peronosporales,Pseudoperonospora, Albugo occidentalis, Phytophthora spp., Pythium,Bremia and other pathogens.

What is claimed is:
 1. A fungicidal two- or three-component compositionbased on metalaxyl, wherein more than 70% by weight of the metalaxyl isthe R-enantiomer (I) and the composition comprises as the furthercomponent: IIA) mancozeb, IIB) chlorothalonil, IIC) a copper salt, IID)folpet, IIE) fluazinam or IIF) cymoxanil, it being possible when IIF) isused for a third component selected from IIA to IIE also to be present.2. A composition according to claim 1, wherein the ratio by weight ofI:II is from 10:1 to 1:100, preferably from 5:1 to 1:30.
 3. Acomposition according to claim 1, wherein the metalaxyl has anR-enantiomer content of more than 85% by weight.
 4. A compositionaccording to claim 3, wherein the metalaxyl has an R-enantiomer contentof more than 92% by weight.
 5. A composition according to claim 4,wherein there is used pure R-metalaxyl that is substantially free ofS-enantiomer.
 6. A composition according to claim 1, wherein mancozeb(IIA) is used as the second component of the mixture with R-metalaxyl ina ratio by weight of from 1:1 to 1:20.
 7. A composition according toclaim 1, wherein chlorothalonil (IIB) is used as the second component ofthe mixture with R-metalaxyl in a ratio by weight of from 2:1 to 1:12.8. A composition according to claim 1, wherein a fungicidal copper salt(IIC) is used as the second component of the mixture with R-metalaxyl ina ratio by weight of from 5:1 to 1:30.
 9. A composition according toclaim 8, wherein the copper salt is copper hydroxide.
 10. A compositionaccording to claim 1, wherein folpet (IID) is used as the secondcomponent of the mixture with R-metalaxyl in a ratio by weight of from3:1 to 1:10.
 11. A composition according to claim 1, wherein fluazinam(IIE) is used as the second component of the mixture with R-metalaxyl ina ratio by weight of from 5:1 to 1:20.
 12. A composition according toclaim 1, wherein cymoxanil (IIF) is used as the second component of themixture with R-metalaxyl in a ratio by weight of from 6:1 to 1:6.
 13. Acomposition according to claim 12, wherein in addition to R-metalaxyl(I) and cymoxanil (IIF) there is used as a third component mancozeb(IIA) in ratios by weight of I:IIF:IIA=1 to 7:1:4 to
 10. 14. Acomposition according to claim 12, wherein in addition to R-metalaxyl(I) and cymoxanil (IIF) there is used as a third component folpet (IID)in ratios by weight of I:IF:IID=1 to 7:1:2 to
 8. 15. A method ofcontrolling and preventing Oomycetes infestation in plants, parts ofplants or at the site of their growth, which comprises applying in anydesired sequence, simultaneously or in immediate succession, metalaxylhaving an R-enantiomer content of more than 70% by weight and a furtherfungicidal component selected from mancozeb (IIA), chlorothalonil (IIB),a copper salt (IIC), folpet (IID), fluazinam (IIE) and cymoxanil (IIF).16. A method according to claim 15, wherein when cymoxanil (IIF) isused, there is additionally used as a third component one of thecomponents mentioned for IIA to IIE.
 17. A method according to claim 15,wherein the R-enantiomer content of the metalaxyl used is more than 85%by weight.
 18. A method according to claim 17, wherein the R-enantiomercontent of the metalaxyl used is more than 92% by weight.
 19. A methodaccording to claim 18, wherein pure R-metalaxyl that is substantiallyfree of S-enantiomer is used as the metalaxyl component.
 20. A methodaccording to claim 15, wherein Phytophthora spp., Plasmopara, Pythium,Pseudoperonospora, Albugo occidentalis and/or Bremia are controlled.